1. Field of the Invention
The invention relates to a throttle element for incorporation into a fuel-carrying conduit, and to an injection pump embodying such a throttle element.
2. Description of the Prior Art
A throttle element embodied as an insert, for incorporation into a fuel-carrying conduit with a throttle and a filter collar, which is secured in the conduit with a thread, is known.
Because of the thread and because of the necessity of being able to exert a tightening torque on the throttle element, this throttle element is relatively large in structure. Furthermore, producing the thread in the conduit and in the throttle element and the production of a screw head, such as a hexagonal socket head, entails cost.
The object of the invention is furnish a throttle element with a gap filter that can be produced economically, is compact in structure, is favorable from a production standpoint, and can be mounted simply and reliably.
According to the invention, this object is attained by a throttle element for incorporation into a fuel-carrying conduit, having a throttle by which a fluid flow flowing through the throttle element can be limited, the throttle element being embodied as an insert and having a sealing portion that cooperates with the conduit, and a passage having a throttle is provided between the two sides of the sealing portion, and a filter collar that with the conduit forms an annular gap is present on the throttle element, and the throttle element is press-fitted into the conduit.
By means of the throttle element of the invention, the incorporation into the fuel-carrying conduit is facilitated; neither a female thread in the conduit nor a male thread in the throttle element has to be cut, which simplifies production. Furthermore, the throttle element can be made shorter, which widens its utility and further reduces the costs for the conduit, which is now shorter. These advantages are especially significant because these involve large-scale mass-produced items in which even small savings per item add up to large amounts.
Furthermore, because of the press fit between the throttle element and the conduit, precise positioning of the throttle element in the conduit is attained and thus the tightness is improved. In a version involving screwing with a thread, the location of the throttle element in the conduit cannot be replicated with the same accuracy.
In a further feature of the invention, the sealing portion is embodied as a cylindrical collar or a conical collar, making simple production with optimal sealing action attainable. In the case of a conical collar, the production tolerance can be increased somewhat without any sacrifice in terms of tightness.
In a further feature of the invention, the sealing portion is embodied as a truncated cone, which cooperates with a corresponding sealing seat in the conduit, so that the sealing action of the sealing portion is virtually independent of the diameter of the sealing portion.
In further variants of the invention, it is provided that the throttle element has a centering collar with a fluid passage, and/or that the centering collar is chamfered, and that the fluid passage is embodied as a flat face, so that tilting of the throttle element upon mounting is precluded.
In a further feature of the invention, the throttle element has a sleeve, and the sleeve is upset in the pressing process, so that the throttle element can be secured in the conduit in prestressed fashion, and thus even over a long service life, the sealing action and the function of the throttle element are assured.
The object stated above is also attained by an injection pump, having a low-pressure region and a high-pressure region, having a conduit for removing leaking oil from the low-pressure region, and having a throttle element according to the invention so that the injection pump has a leaking oil removal that has the advantages of the invention. In injection pumps, the pumping quantity of the high-pressure region is regulated by an intake throttle restriction. The metering valves employed have a certain leakage in the closed state, and in the overrunning mode of the engine this leads to a gradual increase in pressure on the intake side of the high-pressure fuel pump and thus causes it to begin pumping. To prevent this, between the intake side of the high-pressure fuel pump, corresponding to the low-pressure region of the injection pump, and the pressureless fuel return, a throttle, the so-called zero-feed throttle, is provided, by way of which the leakage from the low-pressure region is removed. By the use of a throttle according to the invention as a zero-feed throttle, the aforementioned advantages can be achieved.
In further features of the invention, the conduit has a graduated diameter, and the transition between the diameters is embodied as a sealing seat, or a closure body is press-fitted into the conduit, and the closure body exerts a pressing force on the sleeve of the throttle element. In these versions, reliable sealing between the throttle element and the conduit is assured, regardless of the production tolerances of the throttle element. Because the closure body exerts a pressing force on the sleeve of the throttle element, an adequately high pressure per unit of surface area between the sealing faces of the throttle element and the conduit is assured under all operating conditions.